Conventional coiled filaments of an X-ray tube have a close wound helical form, suspended in a channel, as shown in FIG. 1. A longitudinal view of the coil is shown in FIG. 2. Generally, the filament coil faces the anode of the tube, and the geometry of the electric field tends to spread, particularly near the filament coil where the electron energy is still low, leading to a spreading of the electron beam; and thus, reducing the electron beam intensity delivered to the anode. The spreading of the beam from a cathode surface with a convex curvature facing the anode, as shown in FIG. 2, is a well-known property of geometry for cylindrical filament coils. It should be noted that the spreading in FIG. 2 is exaggerated for accent. Spreading of the electron beam increases the width of the electron beam incident on the anode, decreases uniformity within the electron beam incident on the anode, and blurs the edge of the electron beam incident on the anode.